When the cargo hold in an aircraft is being loaded with containers, pallets or similar items of freight, the containers are conveyed into the aircraft cargo hold through a door 12, as is shown in the attached FIG. 6. In the process, the containers 10 first enter the cargo hold by rolling along ball mats 14, being driven by power drive units 18 that operate in a direction perpendicular to the long axis of the aircraft, and are then conveyed to the final storage site on roller tracks that run in the long direction of the aircraft. They are retained there by latch units 24 that engage the container's lower edges 20. Such an arrangement is disclosed in the German patent 2 161 735; the latch units described in that document are initially lowered by hand into a retracted state before loading, so that the containers can roll over them, and only thereafter are manually brought into the locking position, when the containers are standing in the right place.
To prevent damage from being caused by latch units that have accidentally been left in the raised position, latch units have been designed such as are described, e.g., in German patent DE 195 44 796 C1; when a moving container encounters such a unit, the unit is pressed downward in a direction perpendicular to the locking position, i.e. perpendicular to the edge of the container that would otherwise be engaged by the unit.
The problem is especially critical in the region near the door to the cargo hold, because relatively long items of freight or certain kinds of containers are rotated while in this region and must then be transported further in a direction 90° away from the direction in which they entered. Because of this turning movement of the freight items, the latch units present in this region must be fixed mechanically in their retracted resting position.
Another problem is that during loading and unloading of the cargo hold in an aircraft, the floor of the hold may be tilted or unintended movements of the freight may be caused in other ways, with the result that the freight can roll out of the storage hold through the door and thus endanger the personnel working there.